A cleaning device and cleaning method for denitration catalyst
By combining roller brush, spraying and blowing technologies in the denitrification catalyst cleaning device, the catalyst cleaning problems in the prior art are solved, efficient and environmentally friendly catalyst cleaning is achieved, and service life is extended and secondary pollution is avoided.
Patent Information
- Application Number
- CN202211194523.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2022-09-29
- Publication Date
- 2024-12-13
- Estimated Expiration
- 2042-09-29
AI Technical Summary
The prior art is difficult to efficiently, thoroughly, energy-saving and environmentally friendly to clean flue gas denitrification catalysts, especially in the removal of dust and scale on the surface of the catalyst or honeycomb holes, which have problems of secondary pollution and resource waste.
A denitrification catalyst cleaning device is designed, including a rolling brush mechanism, a spray mechanism and a spray mechanism. Through physical friction, spraying and soaking in the dry state, combined with a vibration motor and friction protrusion, the catalyst surface and honeycomb are realized. Efficient cleaning in the holes to avoid secondary pollution.
It achieves efficient and thorough cleaning of the catalyst, removes dust and scale from the surface and honeycomb holes, extends the service life of the catalyst, and avoids waste of resources and environmental pollution.
Smart Images
Figure CN115582321B_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of denitration catalyst cleaning, in particular to a denitration catalyst cleaning device and a cleaning method thereof. Background Art
[0002] The promulgation of the "Emission Standards for Air Pollutants from Thermal Power Plants" means that flue gas denitrification will become the focus of environmental protection projects in thermal power plants in my country. The most widely used denitrification technology is the selective catalytic reduction (SCR) method, the core of which is the SCR denitrification catalyst. It is not only expensive, but its cost accounts for about 40% of the comprehensive cost of the denitrification project. The performance of the catalyst directly determines the denitrification efficiency and nitrogen oxide emissions, ammonia escape, SO2 / SO3 conversion rate, system pressure, power consumption, reducing agent consumption, etc. of the SCR flue gas denitrification system. The service life of the SCR catalyst for general industrial applications is 24,000 hours, and it needs to be replaced or regenerated in time after the expiration. SCR catalyst regeneration can avoid serious waste of resources and secondary pollution of the environment, and has significant economic and environmental benefits. Therefore, denitrification catalyst regeneration is the only way for the development of the SCR denitrification industry.
[0003] The regeneration methods of SCR flue gas denitration catalysts include water washing regeneration, thermal regeneration, thermal reduction regeneration, acid regeneration, SO2 acidification thermal regeneration, active salt solution activation regeneration and other methods. However, no matter which regeneration method is used, efficient and thorough cleaning of the catalyst blocks removed from the denitration system is a prerequisite and a necessary condition. This step directly affects the effect of catalyst regeneration. However, due to the large amount of smoke and scaling / coke accumulated on the surface or in the honeycomb pores of the denitration catalyst, it becomes a difficult task to thoroughly clean the denitration catalyst. The goal of the present invention is to complete the cleaning step of the denitration catalyst efficiently, energy-saving and environmentally friendly. Summary of the invention
[0004] The purpose of the present invention is to provide a cleaning device and a cleaning method for a denitration catalyst, which not only provides a highly efficient, thorough, energy-saving and environmentally friendly clean denitration catalyst assembly, but also a fully enclosed system that effectively avoids secondary pollution and is more convenient to transport and use.
[0005] To achieve the above-mentioned purpose, the present invention designs a cleaning device for a denitrification catalyst, comprising a cleaning box, a loading and unloading port is provided on the front side of the cleaning box, a sealing door is hinged on one side of the loading and unloading port, a plurality of ash leakage holes are provided on the bottom surface of the cleaning box, supporting legs are respectively provided at the four corners of the bottom of the cleaning box, an ash hopper is provided below the cleaning box, a rolling brush mechanism and a spray mechanism are provided on the inner wall of the cleaning box, and a blowing mechanism is provided on the top of the cleaning box.
[0006] Preferably, a vibration motor is provided on one side of the bottom of the cleaning box.
[0007] Preferably, a plurality of friction protrusions are provided on the bottom surface of the cleaning box, and the friction protrusions are spaced apart from the ash leakage holes.
[0008] Preferably, the roller brush mechanism includes a plurality of vertically arranged brushes evenly embedded on the inner wall of the cleaning box, the brushes are arranged on the inner wall of the cleaning box by rotating brush rollers, and each brush roller is transmission connected, one of the brush rollers rotates to extend above the cleaning box and is connected to a driven bevel gear, a reduction motor is arranged on the top of the cleaning box, and an active bevel gear meshing with the driven bevel gear is connected to the output shaft of the reduction motor.
[0009] Preferably, the spray mechanism includes a plurality of spray pipes arranged on the inner wall of the cleaning box and nozzles arranged on the spray pipes, the spray pipes and the brushes are arranged at intervals, a water supply pipe is provided on the periphery of the cleaning box, the water supply pipe is connected to a water inlet pipe, a water supply valve is provided on the water inlet pipe, and the water supply pipe is connected to each spray pipe.
[0010] Preferably, the blowing mechanism includes a plurality of spray pipes arranged transversely at the top of the cleaning box, a spray head arranged on each spray pipe, an air supply pipe is arranged longitudinally at the top of the cleaning box, the air supply pipe is connected to an air intake pipe connected to an air source, a blowing valve is arranged on the air intake pipe, and the air supply pipe is connected to each spray pipe.
[0011] A cleaning method using a denitration catalyst cleaning device comprises the following steps:
[0012] S1: First, open the sealed door, place the denitration catalyst vertically on the bottom of the cleaning box from the access port, and close the sealed door;
[0013] S2: Cleaning in dry state: Turn on the drive motor, the brush roller starts to roll and drives the brush to clean the dirt on the catalyst surface; turn on the spray valve, and the spray airflow directly targets the honeycomb porous structure of the catalyst for enhanced cleaning; turn on the vibration motor, and the vibration condition will enhance the force to remove the dirt on the catalyst surface. The friction protrusions on the bottom surface of the cleaning box can effectively increase the friction and enhance the cleaning effect, so as to clean the dirt on the surface of the denitration catalyst without water in a dry state. The cleaning time is 30min-3h;
[0014] S3: Clean water spraying: Connect the water inlet pipe to the high-pressure water source, open the water supply valve of the spray mechanism, and make the nozzle on the spray pipe spray the denitrification catalyst with clean water. The flushing time is 30min-1h;
[0015] S4: Pre-cleaning by soaking in clean water: Close the outlet of the ash hopper, open the water supply valve of the spray mechanism, immerse the catalyst in clean water, and soak for 1-5 hours. While soaking, turn on the vibration motor to quickly remove the dirt on the catalyst. At the same time, turn on the drive motor to rotate the brush to remove the dirt on the catalyst surface, and clean the hard-to-remove materials on the catalyst surface in a wet state;
[0016] S5: Active cleaning liquid immersion cleaning: Introduce active cleaning liquid into the water inlet pipe, open the water supply valve, immerse the catalyst in the active cleaning liquid, and then turn on the drive motor and the vibration motor. In the active cleaning liquid immersion state, use the brush to roll and clean the denitration catalyst for 30 minutes to 10 hours. Combined with the vibration effect, it can effectively remove the coking and residual dust and other difficult-to-remove substances on the denitration catalyst;
[0017] S6: Soak in clean water: drain the active cleaning liquid, connect a high-pressure water source to the water inlet pipe, and open the water inlet valve. Spray the denitrification catalyst with clean water until the catalyst is submerged. Soak for 30 minutes to 2 hours to thoroughly clean the denitrification catalyst. Then open the ash hopper, drain the soaking water, and complete the cleaning of the denitrification catalyst.
[0018] The beneficial effects of the present invention are:
[0019] 1. The present invention provides a roller brush mechanism in the cleaning box, so that the catalyst surface can be cleaned by physical friction of the roller brush in a dry state; a vibration motor is provided on one side of the bottom of the cleaning box, so that the ability to clean dust on the catalyst surface can be enhanced under the action of high-frequency vibration; a blowing mechanism is provided on the top of the cleaning box, so that the airflow ejected by the injection head can directly clean the honeycomb porous structure of the catalyst efficiently; the above multiple effects are superimposed, so that dust on the surface and in the honeycomb holes can be effectively removed.
[0020] 2. The present invention provides a spraying mechanism on the inner wall of the cleaning box, so that the catalyst can be sprayed and soaked with clean water, thereby removing some dust that is difficult to peel off; it can also be immersed in the activator, which can thoroughly and efficiently remove the coking and residual dust on the catalyst. Finally, the catalyst is soaked in clean water to thoroughly clean the surface of the catalyst and remove the residues of impurities such as active solvents, thereby achieving efficient cleaning of the denitrification catalyst. By closed cleaning in the cleaning box, secondary pollution can be effectively avoided, which is convenient for transportation and use. BRIEF DESCRIPTION OF THE DRAWINGS
[0021] Figure 1 It is a schematic diagram of the overall structure of the present invention;
[0022] Figure 2 It is a cross-sectional structural schematic diagram of the present invention;
[0023] Figure 3 It is a rear view structural schematic diagram of the present invention;
[0024] Figure 4 It is a schematic diagram of the internal structure of the cleaning box, which is used to show the transmission connection method of the brush roller;
[0025] Figure 5 It is a schematic diagram of the pipeline connection structure of the injection mechanism;
[0026] Figure 6 It is a structural schematic diagram of the bottom surface of the cleaning box, which is used to show the positional relationship between the ash leakage holes and the friction protrusions;
[0027] Figure 7 is a flow chart of the cleaning method of the present invention;
[0028] Figure 8 is a flow chart of another embodiment of the cleaning method of the present invention;
[0029] The numbers in the figure are: 1 cleaning box, 2 sealing door, 3 spray valve, 4 air inlet pipe, 5 driven bevel gear, 6 driving bevel gear, 7 driving motor, 8 water supply pipe, 9 ash hopper, 10 supporting leg, 11 vibration motor, 12 ash leakage hole, 13 friction protrusion, 14 brush, 15 spray pipeline, 16 nozzle, 17 air supply pipe, 18 spray head, 19 brush roller, 20 spray pipe, 21 water inlet pipe. DETAILED DESCRIPTION
[0030] The preferred embodiments of the present invention are described below in conjunction with the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.
[0031] Example 1
[0032] A cleaning device for a denitration catalyst, such as Figures 1 to 6 As shown, it includes a cleaning box 1, a loading and unloading port is opened on the front side of the cleaning box 1, a sealing door 2 is hinged on one side of the loading and unloading port, a plurality of ash leakage holes 12 are opened on the bottom surface of the cleaning box 1, and a plurality of friction protrusions 13 are arranged on the bottom surface inside the cleaning box 1, and the friction protrusions 13 and the ash leakage holes 12 are arranged alternately at intervals. The friction protrusions 13 can effectively increase the friction between the denitration catalyst and the bottom surface of the cleaning box 1, and further enhance the cleaning effect; support legs 10 are respectively provided at the four corners of the bottom of the cleaning box 1, and an ash hopper 9 is provided under the cleaning box 1. The ash hopper 9 is used to collect dust and dirt, and a sealing plate can be provided at the discharge port of the ash hopper to prevent dust and dirt from leaking.
[0033] A vibration motor 11 is provided at one side of the bottom of the cleaning box 1. The vibration motor 11 can make the denitration catalyst vibrate when cleaning, which can effectively enhance the ability of the denitration catalyst to remove dust and dirt on its surface under vibration conditions.
[0034] A rolling brush mechanism and a spraying mechanism are provided on the inner wall of the cleaning box 1. The rolling brush mechanism includes a plurality of vertically arranged brushes 14 uniformly embedded on the inner wall of the cleaning box 1, and the brushes 14 are in contact with the denitration catalyst. The brushes 14 are arranged on the inner wall of the cleaning box 1 through a brush roller 19, and each brush roller 19 is connected to each other by transmission, which can be achieved by a sprocket chain transmission method. One of the brush rollers 19 rotates to extend above the cleaning box 1 and is connected to a driven bevel gear 5. A reduction motor 7 is provided on the top of the cleaning box 1, and an active bevel gear 6 meshing with the driven bevel gear 5 is connected to the output shaft of the reduction motor 7. The arrangement of the brush 14 allows the brush 14 to roll and clean the denitration catalyst, and the cleaning effect is better.
[0035] The spray mechanism includes a plurality of spray pipelines 15 provided on the inner wall of the cleaning box 1 and a nozzle 16 provided on the spray pipeline 15. The spray pipeline 15 and the brush 14 are arranged at intervals. A water supply pipeline 8 is provided on the periphery of the cleaning box 1. The water supply pipeline 8 is connected to a water inlet pipe 21. A water supply valve is provided on the water inlet pipe 21. The water supply pipe 8 is connected to each spray pipeline 15. The high-pressure water source pipeline or the active cleaning liquid pipeline can be switched on the water inlet pipe 21. The switching between the two can be achieved by setting a three-way pipe. The spray pipeline 15 is used to spray and clean the denitration catalyst.
[0036] A spray mechanism is provided at the top of the cleaning box, and the spray mechanism includes a plurality of spray pipes 20 arranged transversely at the top of the cleaning box 1, and a spray head 18 arranged on each spray pipe 20. An air supply pipe 17 is longitudinally provided at the top of the cleaning box 1, and an air intake pipe 4 connected to an external air source is connected to the air supply pipe 17. A compressed air bag can be externally connected to the air intake pipe 4 to provide an air source to the spray pipe 20. A spray valve 3 is provided on the air intake pipe 4, and the air supply pipe 17 is connected to each spray pipe 20. The spray pipe 20 can directly spray airflow to the catalyst, and can perform enhanced cleaning on its honeycomb hole structure.
[0037] Example 2
[0038] A method for cleaning a denitration catalyst, such as Figure 7 As shown, the following steps are included:
[0039] S1: First, open the sealed door 2, place the denitration catalyst vertically on the bottom surface of the cleaning box 1 from the access port, and close the sealed door 2; so that the denitration catalyst can effectively avoid secondary pollution in a sealed state and is easy to transport.
[0040] S2: Cleaning in dry state: Turn on the reduction motor 7, the brush roller 19 starts to roll and drives the brush 14 to clean the dust on the surface of the catalyst; turn on the spray valve 3, and spray the airflow through the spray head 18 on the spray pipe 20 to directly strengthen the cleaning of the honeycomb porous structure of the catalyst; turn on the vibration motor 11 to enhance the force of removing dust on the catalyst surface under vibration conditions, and cooperate with the friction protrusions 13 on the bottom surface of the cleaning box 1 to effectively increase the friction and enhance the cleaning effect, so as to perform waterless cleaning on the surface of the denitration catalyst in a dry state, and the cleaning time is 30min-3h; after completing one cleaning, the catalyst can be turned over to make the position that was originally inaccessible to the brush for thorough cleaning; repeat the above-mentioned dry cleaning steps until the denitration catalyst is completely cleaned.
[0041] S3: Clean water spraying: connect the water inlet pipe 21 to the high-pressure water source pipeline, open the water supply valve of the spray mechanism, and make the nozzle 16 on the spray pipeline 15 spray the denitration catalyst with clean water for 30 minutes to 1 hour; wash away the dust and dirt on the surface of the denitration catalyst.
[0042] S4: Pre-cleaning by soaking in clean water: block the outlet of the ash hopper 9, open the water supply valve of the spray mechanism, immerse the catalyst in clean water, and soak for 1-5 hours. While soaking, turn on the vibration motor 11 to quickly remove the dust on the catalyst. At the same time, turn on the reduction motor 7 to rotate the brush 14 to remove the dust on the catalyst surface, and clean the hard-to-peel-off materials on the catalyst surface in a wet state;
[0043] S5: Immersion cleaning with active cleaning liquid: connect the water inlet pipe 21 with the active cleaning liquid pipeline. The active cleaning liquid is an inorganic acid compound. Open the water supply valve to immerse the catalyst in the active cleaning liquid. Then turn on the reduction motor 7 and the vibration motor 11. In the state of active cleaning liquid immersion, make the brush 14 roll and clean the denitration catalyst for 30min-10h. Combined with the vibration effect, it can effectively remove the coking and residual dust on the denitration catalyst. The hard-to-remove substances; in this step, according to the component analysis of the dust on the catalyst label, the effective compounding agent such as the inorganic alkali compounding agent can be replaced.
[0044] S6: Soaking in clean water: drain the active cleaning liquid, switch to the high-pressure water source pipeline on the water inlet pipe 21, and open the water supply valve, spray the denitration catalyst with clean water until the catalyst is immersed, soak for 30min-2h, thoroughly clean the denitration catalyst, then open the ash hopper 9, drain the soaking water, and complete the cleaning of the denitration catalyst.
[0045] Example 3
[0046] A method for cleaning a denitration catalyst, such as Figure 8 As shown, the difference from Example 2 is that the following steps are included:
[0047] S1: First, open the sealed door 2, place the denitration catalyst vertically on the bottom surface of the cleaning box 1 from the access port, and close the sealed door 2; so that the denitration catalyst can effectively avoid secondary pollution in a sealed state and is easy to transport.
[0048] S2: Cleaning in dry state: Turn on the reduction motor 7, the brush roller 19 starts to roll and drives the brush 14 to clean the dust on the surface of the catalyst; turn on the spray valve 3, and spray the airflow through the spray head 18 on the spray pipe 20 to directly strengthen the cleaning of the honeycomb porous structure of the catalyst; turn on the vibration motor 11, and enhance the force of removing dust on the catalyst surface under vibration conditions, and cooperate with the friction protrusions 13 on the bottom surface of the cleaning box 1 to effectively increase the friction and enhance the cleaning effect, so as to perform waterless cleaning on the surface of the denitration catalyst in a dry state, and the cleaning time is 30min-3h; after completing one cleaning, the catalyst can be turned over to make the position that was originally inaccessible to the brush for thorough cleaning; repeat the above-mentioned dry cleaning steps until the denitration catalyst is completely cleaned.
[0049] S3: Pre-cleaning by soaking in clean water: Seal the outlet of the ash hopper 9, open the water supply valve of the spray mechanism, immerse the catalyst in clean water, and soak for 1-10 hours. At the same time, turn on the vibration motor 11 to quickly peel off the dust on the catalyst. At the same time, turn on the reduction motor 7 to rotate the brush 14 to remove the dust on the catalyst surface. Prolong the soaking time and clean the hard-to-peel-off materials on the catalyst surface in a wet state. In this step, according to the component analysis of the dust on the catalyst label, an effective compounding agent such as an inorganic alkali compounding agent can be replaced.
[0050] S4: Active cleaning liquid immersion cleaning: connect the water inlet pipe 21 with the active cleaning liquid pipeline, the active cleaning liquid is an inorganic acid compound, open the water supply valve, immerse the catalyst in the active cleaning liquid, and then turn on the reduction motor 7 and the vibration motor 11. In the active cleaning liquid immersion state, make the brush 14 roll and clean the denitration catalyst for 30min-10h. Combined with the vibration effect, it can effectively remove the coking and residual dust and other substances that are difficult to remove on the denitration catalyst;
[0051] S5: Soak in clean water: drain the active cleaning liquid, switch to the high-pressure water source pipeline on the water inlet pipe 21, and open the water supply valve, spray the denitrification catalyst with clean water until the catalyst is immersed, soak for 30min-2h, thoroughly clean the denitrification catalyst, then open the ash hopper 9, drain the soaking water, and complete the cleaning of the denitrification catalyst.
[0052] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.
Claims
1. A method for cleaning a denitration catalyst, which is implemented based on a denitration catalyst cleaning device, wherein the denitration catalyst cleaning device comprises a cleaning box (1), It is characterized in that A take-in / take-out opening is provided on the front side of the cleaning box (1), a sealing door (2) is hinged on one side of the take-in / take-out opening, a plurality of ash leakage holes (12) are provided on the bottom surface of the cleaning box (1), support legs (10) are provided at the four corners of the bottom of the cleaning box (1), an ash hopper (9) is provided below the cleaning box (1), and a rolling brush mechanism and a spray mechanism are provided on the inner wall of the cleaning box (1); The roller brush mechanism comprises a plurality of vertically arranged brushes (14) uniformly embedded on the inner wall of the cleaning box (1); the brushes (14) are rotatably arranged on the inner wall of the cleaning box (1) via brush rollers (19); and each brush roller (19) is transmission-connected to each other; one of the brush rollers (19) is rotatably extended above the cleaning box (1) and is connected to a driven bevel gear (5); a reduction motor (7) is arranged on the top of the cleaning box (1); and an active bevel gear (6) meshing with the driven bevel gear (5) is connected to the output shaft of the reduction motor (7); The spray mechanism comprises a plurality of spray pipelines (15) arranged on the inner wall of the cleaning box (1) and a spray head (16) arranged on the spray pipelines (15); the spray pipelines (15) and the brushes (14) are arranged at intervals; a water supply pipeline (8) is arranged on the periphery of the cleaning box (1); a water inlet pipe (21) is connected to the water supply pipeline (8); a water supply valve is arranged on the water inlet pipe (21); and the water supply pipeline (8) is connected to each spray pipeline (15); A blowing mechanism is provided at the top of the cleaning box (1), the blowing mechanism comprising a plurality of spray pipes (20) arranged transversely at the top of the cleaning box (1), and a spray head (18) arranged on each spray pipe (20); an air supply pipe (17) is longitudinally provided at the top of the cleaning box (1); an air intake pipe (4) connected to an external air source is connected to the air supply pipe (17); a blowing valve (3) is provided on the air intake pipe (4); and the air supply pipe (17) is in communication with each spray pipe (20); A plurality of friction protrusions (13) are provided on the bottom surface of the cleaning box (1), and the friction protrusions (13) are spaced apart from the ash leakage holes (12); The specific steps include: S1: First, open the sealed door (2), vertically place the denitration catalyst from the access opening on the bottom surface of the cleaning box (1), and close the sealed door (2); S2: Cleaning in dry state: Turn on the reduction motor (7), and the brush roller (19) starts to roll and drives the brush (14) to clean the dirt on the surface of the catalyst; turn on the spray valve (3), and spray the airflow directly to the honeycomb porous structure of the catalyst through the nozzle on the spray pipe (20) to strengthen the cleaning; turn on the vibration motor (11), and enhance the force of removing dirt on the surface of the catalyst under vibration conditions, and cooperate with the friction protrusions (13) on the inner bottom surface of the cleaning box (1) to effectively increase the friction force and enhance the cleaning effect, so as to perform waterless cleaning on the surface of the denitration catalyst in a dry state, and the cleaning time is 30 minutes to 3 hours; S3: pre-cleaning by soaking in clean water: seal the outlet of the ash hopper (9), open the water supply valve of the spray mechanism, immerse the catalyst in clean water, and soak for 1-5 hours. At the same time, turn on the vibration motor (11) to quickly remove the dust on the catalyst. At the same time, turn on the reduction motor (7) to rotate the brush (14) to remove the dust on the catalyst surface, and clean the hard-to-remove materials on the catalyst surface in a wet state; S4: Active cleaning liquid soaking and cleaning: Active cleaning liquid is introduced into the water inlet pipe (21), and the water supply valve is opened to immerse the catalyst in the active cleaning liquid. Then, the reduction motor (7) and the vibration motor (11) are turned on. In the active cleaning liquid soaking state, the brush (14) is used to roll and clean the denitration catalyst for 30 minutes to 10 hours. Combined with the vibration effect, the coke and residual dirt on the denitration catalyst can be efficiently removed; S5: Soaking in clean water: drain the active cleaning liquid, connect a high-pressure water source to the water inlet pipe (21), open the water inlet valve, spray the denitration catalyst with clean water until the catalyst is submerged, soak for 30 minutes to 2 hours, thoroughly clean the denitration catalyst, then open the ash hopper (9), drain the soaking water, and complete the cleaning of the denitration catalyst.
2. The method for cleaning the denitration catalyst according to claim 1, Features: A vibration motor (11) is provided on one side of the bottom of the cleaning box (1).
3. A method for cleaning a denitration catalyst as claimed in claim 1, Features: Before pre-cleaning by soaking in clean water, spray with clean water: connect the water inlet pipe (21) to a high-pressure water source, open the water supply valve of the spray mechanism, and allow the nozzle (16) on the spray pipe (15) to spray the denitrification catalyst with clean water for 30 minutes to 1 hour.